Telephone system



Aug. 24 ,1926. 1,596,901

M. B. STAZAK TELEPHQNE SYSTEM I med JungZQ mm 2 Sheets-Sheet 1 I. baa/55m Aug. 24,1926. 1,596,901 M. B. sT zAK 5 TELEPHONE SYSTEM Filed June 25, 1923 2 Sheets-Sheet 2 Patented Aug. 24, 1926.

mitten star Mil-6,991

clerics MICHAEL B. STAZAK, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWlITGHBOAB/D AND SUPPLY COMPANY, OF CHICAGO, ILLINCBIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Application filed June 25, 1923. serial No. 647,451.

My invention relates to telephone systems in which manually. operated link circuits are employed for interconnecting subscribers telephone lines as calling and called lines, and particularly to systems embodying automatic features.

A feature of my invention is the provision of a link circuit for interconnecting subscribers lines of the same exchange in conversational circuit and also the provision of a trunk circuitto which my link circuit is adapted to be operatively connected to connect a subscribers line at one Xchange with a subscribers line ofanother exchange. The link circuit of my invention is provided with automatic disconnect .means for automatically freeing the calling subscribers line from the link circuit after a connection has been established between a calling subscribers line and another subscribers line .at the same exchange as a called line, immediately upon the replacement. ofithe calling subscribers receiver .upon its switchhook. The calling subscribers line is now ready to be called, or to initiate another call which may be seized by any one of the operators before whom the call is distributed.

.Another feature of myinvention is the provision of means for rendering theautomatic disconnect means in my cord circuit, ineti'ective when my link circuit is connected to my trunk circuit to extend a call to a distant exchange and-the further provision of means in my link circuit for automatically flashing a supervisory signal after the calling sub scriber replaces his receiver upon its switchhook and again removesit to initiate another call or recalhbefore the link circuit is disconnected from the calling subscribers line,

to attract the attention of the operator-controlling t is link cn'cuit which will be the same operator that handled the preceding.

call initiated by the calling subscriber.

Another feature of my invention is the provision of means for providing secret service on the link circuit between a calling and called subscriber when a local connection is established, and the provision of means for permitting the operator controlling the link circuit to listen in on the conversation when trunk connection is established.

Still a further feature of my invention is he provision of means for permitting ringngcurrentto be applied from the exchange n which the calling sub'scribers line termie i i nates to signal the called subscriber at the distant exchange.

' Another feature of my invention is the provlsion of a pilot signal and means for automatically flashing the same when a call is made by the. calling subscriber after the completion of a trunk connection.

The above mentioned features as well as other features not specifically pointed out above, will be more fully andparticularly pointed out in the ensuing specification and claims, reference being had to the accompanying drawings in which Fig. 1 illustrates the cord circuit of my invention and also shows two common battery subscriber substations terminating in well known line circuits, and

Fig. 2 illustrates the trunk circuit of my invention which is adapted to work in connection with my cord circuit. V

' Referring now in general to my invention, as illustrated in Fig. 1, it comprises a well known common battery, calling substation A, terminating at the exchange in a well.

known line circuit L comprising multiple answering jacks J, multiple line lamps S, a line relay LR for controlling the operation ofthe line lamp signals S, and a cut off relay CO. To the right of the drawing,l

show a common battery called subscribers substation B, terminating at the exchange in a l ne circuit L, which comprises, multiple.

answering jacks J, multiple line lamps S,

ranged to interconnect the subscribers substations A and B, and also to interconnect substation A and a substation D at a distant exchange via my trunkcircuit TC shown in Fig.2. 'The cord circuit Gfcomprises an answering plug AP and a calling plug CP interconnected by the heavily marked condurtors, having; the condensers K and I? interposed. The answeringendfc I cord circuit C comprises a sleeve relay SR which energizes in series with the cut oil relay C0 of the line circuit L upon the insertion of the plug AP into one of the jacks J, an answering supervisory lamp AL is also provided which is adapted to serve for several purposes which will be pointed out later. An answering supervisory relay AR is provided for controlling the operation of the supervisory signal AL and link disconnect relay LD and also the relay RR. A pilot signal PS, and a relay PR and interrupter I for interruptingly operating the same are provided. A listening relay LS is also provided and is operable upon the operation of relay SR, to automatically connect the operators telephone set OR- to the talking conductors of my cord circuit C. The relay SR is of such resistance, that it will not operate it another operators cord circuit at another operators position is already connected to one of the multiple jacks J and relay LS in this other cord circuit is energized, for in this case the relay LS, which is of low resistance will shunt the high resistance relay SE of cord circuit C, thereby preventing said relay SE "from energizing, and the failure of relay SR of cord circuit C to energize, relay LS of cord circuit C will not energize to connect the operators set OR to the cord circuit C. This feature will be pointed out more in detail in the ensuing specification.

The calling end of the cord circuit C comprises a sleeve relay SE in series with relay R and is adapted to energize upon the insertion of the plug GP into the trunk ack TJ of my trunk circuit TC. The relay R, is adapted to energize when plug Cl? is connected to one of the jacks J but will not energize when connected to the trunk jack TJ due to the high resistance of relay E of trunk circuit TC. A switching relay SXV is provided and is controlled by relay R for purposes to be pointed out later. A calling supervi ory lamp CL is provided as is also a calling supervisory relay for controlling said lamp CL. A ringing control relay RC and an interrupter relay and interrupter device l are provided for intermittently applying ringing current to the called for subscribers line from any one of the fre quency generators G, G, G and G A key MRK is provided for manually applying ringing current to the called for subscribers line instead of automatically applying ringing current. A recall listening key RLK is provided for purposes to be presently described.

lVhen the cord C is interconnecting two common battery lins such as A and Byrelay R will be energized which in turn causes the operation of relay SW, relay SW when energized opens the energizing circuit of re lay RR whereby said relay RF.- is prevented from operating so long as plug CP is connected to a ack J, since relay SlV will remain energized during the existence of such connection. The relay SW energizing closes a contact in the circuit of the link disconnect relay Ll) and places the said relay LD under the control of the answering supervisory relay AR, so that when the calling subscriber replaces his receiver upon its switchhook, relay AR will deenergize and close a circuit for relay LD whereuponrelay LD will operate to free the calling subscribers line A from the cord circuit C, so that the calling subscriber A may be free to be called or free to initiate a call. which may be seized by any one of the operators in whose position his line terminates even though the plug AP remains in the jack J. Now when my cord circuit C has its calling plug (JP connected to the trunk jack TJ of my trunk circuit TC, relay R will not operate due to the high resistance of relay E in the trunk circuit TC, and relay R tailing to operate, relay SW will not energize whereby the link disconnect relay LD will be rendered ineffective when the calling subscriber at A replaces his receiver upon its switchhook, but relay RR will operate and lock up the lamp AL at this time lightin continuously to notify the operator at that conversation has terminated, but now when the calling subscriber A removes his receiver to initiate a recall or another call, relay AR will again operate to connect the interrupter device I in circuit with the supervisory lamp AL whereupon said signal AL will li ht intermittently to indicate to the operator that another call has been initiated and that her services are desired whereupon she will operate her recall listening key ELK, which will openthe looking circuit of relay RR and at the same time connect the operators set OR to the cord circuit C to enable the operator to converse with the calling subscriber. Relay RR will de-energize when key RLK is operated to its alternate position whereupon the interrupter device I is disconnected out of circuit with lamp A lVhen the device I is connected in circuit with the lamp AL, the pilot lamp PS is also caused to intermittently operatelor supervisory purposes, due to the energization and de-energization of relay PR. l/Vhen trunk connections are 7 established, especially if the trunk connection is atoll connection, it is often desirable to have the calling subscriber be able to recommunicate with the operator that established the original connection, while when local connections are established, it is often desirable to obtain as quick an answer as possible upon recalls. Therefore, to expedite the service the recall is made available to a plurality of operators so that the idle one of a plurality of operators may answer the call.

Referring now to- Fig. 2, it comprises a trunk jack TJ, which is located before the operator at cord circuit G, and with a calling plug GP which is adapted to be connected toa called for subscribers line to extend a call to said called subscribers line When a trunk connectionis desired,the operator at the cord circuit G converses with the operator controlling the trunk circuit TG, over an order wire and the trunk operator will assign a trunk circuit to the operator at cord circuit G, whereupon the operator at cord G will insert her calling plug G? into the trunk jack TJ corresponding to the assigned trunlrcircuit andupon said insertion relay E of trunk TG will energize to close a circuit for relay F whereupon relay F energizes to close a circuit for the signal- TL, which signal will light to notify the operator that the cord G at the calling operatoi"s position has been connected to the proper trunk TG assigned.

I The operator at trunk T G will operate her listening key LEI and test the called for subscribers line to determine its idle or busy condition and if idle will insert plug GP into the 'jack J? whereupon relay SR will energize which will cause relay H to energize to open the circuit of the signal TL to cause the effacement of said signal TL and also to close a normally open contact in the trunk circuit TG. In case the operator of trunk TG inserts the plug GP into jack J before the plug GP cord circuit G is connected to jack J, the signal TL will light so that when plug GP is connected to jack J said signal TL will be eifaced to notify the operator of such connection.

Ringing current will be applied from the cuit G is withdrawn from the jack TJ whereupon relay E will (ls-energize and relay E (lo-energizing relay F will de-energize, thereby causing' the signal TL to light to notify the trunk operator that the connection is no longer desired whereupon she will vithdraw'the plug GP from the jack of the called for subscribers line and the trunk circuit TG will restore to normal.

Having described in general the apparatus employed in a preferred embodiment of my invention, 1 will now describe more in detail the operation of the system as illustrated in the accompanying drawings.

Assuming that the subscriber at substation A initiates a call, the removal of the receiver thereat, establishes an energizing circuit for the line relay LR of the line circuit L, traced from battery through the winding of said relay LR, normal contact station A, normal contact-2 of cut-0E relay GO to ground relay LR energizing over this circuit closes its alternate contact 3 'whereby a circuit is closed for the line signals S which light at different operators positions. The first operator to seize the call by the insertion of her answering plug AP into the jack J before which the signal S is lighted, and assuming that the operator to seize the call is the operator at cord circuit G, a circuit is closed for the sleeve relay SR traced from battery through the winding of said relay SR normal contact l. of relay LD, sleeve contacts of plug AP and jack J, to ground through the winding of cut-o1" relay GO, relay SR and relay GG energizing in series over this circuit. Relay GO upon energizing opens its normal contacts land 2 whereby the line relay LR restores to cause the eifacenient of the line signals S, and the sleeve relay SE of cord circuit G energizing closes an energizing circuit for the listening relay LS traced from battery through the winding of said relay LS, conductor 6, alternate contact 5 of relay SR, normal contact l of relay LD, sleeve contacts of plug AP and jack J to ground through the windsaid relay LS through its alternate contact,

7, conductor 8, normal contact 4 of relay LD, sleeve contacts of plug AP and jack J to ground through the winding of cut-off relay GO. This circuit just traced also forms a shunting circuit about the sleeve relay SR, and the sleeve relay SB will de-energize due to the fact that its winding is of high resistance while the winding of relay LS is oflow resistance. Upon the insertion of the plug AP into the jaclrJ, a circuit is also closed for the answering supervisory relay AR traced from battery through the lower winding of said relay AR, normal contact 9 of relay LD, ring contacts of the plug AP and ack J, through the substation A, tip contact of jack J and plug AP, normal contact 10 of relay Ll), to ground through the upper winding of said relay opens its normally closed contact 11 to pre vent thepremature lighting of the answering supervisory signal AL. Upon the energization of relay LS, the operators telephone head set OR is connected to the talkalternate contacts 12 and 13 of said relay LS and normal contacts l l and 15 of relay SR whereupon the operator inquires the wants of the calling subscriber at substation A.

The feature whereby, all. of the operatorswho atempt to seize the call subsequently to the seizure of the call by the first operator are excludedywill now be explained.

f-Then the first operator to seize the call inserted her answering plug AP into the Relay AR energizing over this circuit ing conductors of thecord circuitG throughjack J, the sleeve relay SR in her cord circuit operated to close a circuit for the listening relay LS whereupon relay LS energized and closed a locking circuit for itself through its alternate contact 7. This locking circuit forming a shunting circuit for the said relay Sl t whereupon said relay SR, due to the high resistance of its winding and the low resistance winding of LS will tie-energize, since sull'icient battery will not flow through said relay SR to maintain the same energized. Now when an operator inserts her answering plug AP into another jack J subsequently to the insertion of the plug Al? into the jack J by the first operator, the sleeve relay Sit in the second operators cord circuit will not operate due to the low resistance path oi the circuit of relay LS of the first cord circuit, and theretore sufficient current will not flow through the high resistance winding of the sleeve relay SE in the second operators cord circuit to operate the same. The failure of relay SR in the second cord circuit to operate, prevents the listening relay LS associated therewith to energize to connect the second operators head set to her cord circuit to enable her to converse over the calling line. The operator receiving no reply to her inquiry will know that the call has been seized by another operator and will then withdraw her answering plug from the multiple jack J.

Referring back to when the operator in quired the wants of the calling subscriber A. and assuming that the calling subscriber A desires to converse with the subscriber at substation B the operator will test the jack J to determine its idle or busy condition in the usual and well known manner. it ssuming the called line is idle the operator will insert the calling plug Cl into the jack J". The insertion of the plug CP into the jack J establishes a circuit for the sleeve relay i R which will energize in series with cut-oil relay CO ot the line circuit L, this circuit being traced from battery through the winding of relay SR, through the Winding of relay R, sleeve contacts of the plug Cl? and jack J, to ground through the winding of cut-off r lay CC of the line circuit L. Relay CO energizes to open its normally closed contacts whereby the line relay LR is removed from the control of the subscriber B so that when suescriber l3 removes his receiver the line signal S will not light. Belay SR upon energizing opens its normally closed contacts 14: and 15 whereby the operators head set OR is disconnected trom the cord circuit C. The winding of relay CC is of low resistance which permits relay R to energize in series with relay SR and said relay CC, said relay R energizing closes its alternate contact. 16 whereby a circuit is closed for the switching relay Sl/V, traced from battery through the winding of said relay SW to ground through the alternate contact 16 of said relay R. Relay Sil upon energizing opens its normally closed contacts and closes its alternate contacts, to prevent the operation of the relay RR and to place the relay Ll) under the control of the calling subscriber A. Relay SR having energized, a circuit is closed for the calling supervisory lamp CL, traced from battery through said lamp CL, normal contact 17 of relay CS, conductor 18 to ground through alternate contact 19 of relay SR, lamp CL lighting over this circuit remains lighted until the called for subscriber removes his receiveritrom its switchhook whereupon relay CS will ener ize to open the circuit or said lamp CL as will be described later.

The plug CP having been inserted into the jack J and relays SlV, SR and R hav ing operated, the operator will depress one ot' the ringing key plungers of the ringing key R-K to connect ringing current of the proper frequency to the called line and assiuning generator G to be of the proper trequency required to operate the call bell at substation B, ringing key plunger 72 will be fully depressed momentarily to close the end spring contact 20 of the ringing key BK thereby closing an energizing circuit for the risging control relay RC, traced from battery through the winding of said relay RC, normal contact 21 of key MRK, conductor 22, the now closed contact 20 of the end spring of. ringing key BK, conductor 23, normal contact 17 of relay CS, conductor 18, to ground through alternate contact 19 of relay SR. Ringing control relay RC energizing over this circuit opens the normally closed contacts 24 and 25 and closes its alternate contacts 24, 26, and 27. The closure of alternate contact 27 establishes a look.

ing circuit for said relay RC which may be traced from battery through the winding of said relay RC, alternate contact 27 of relay RC, conductor 28, normal contact 29 of relay LD, conductor 30, conductor 23, normal contact 17 of relay CS, conductor 18 to ground through alternate contact 19 of relay SR. This circuit just traced places the ringing control relay RC under the control of the calling subscriber A and also under the control of the called subscriber B, so that should the calling subscriber A replace his receiver upon its switchhook before the called subscriber B responds ringing current will be automatically disconnected from the called subscribers line or in case the calling subscriber does not replace his receiver before the called subscriber responds ringing current will be disconnected relay Ll), conductor ing control relay-RC is energized, an energizing circuit is established for the'ringing interrupter relay IR traced from. battery through the live segments of the continuously rotating interrupter device I, through the lower winding of said interrupter re lay IR, conductor. 31, normal contact 32 of key MRK, to ground through alternate contact 26 of relay BC. The interrupter relay IR will energize and de-en-ergize over this circuit due to theinterrupter device I opening and closing the circuit through the lower winding of said relay IR whereby ringing current will be intermittently.applied I interrupter relay IR whereby relay IR. is prevented from further operating to conto the called for subscribers line. v

Assuming that the generator G is of the proper frequency for operating the call bell at the called subscribers substation B the circuit for the ringing current will be. as follows: Ground, through the rotating frequency generator G alternate contact or plunger 6 of the ringing key BK, conductor 34, alternate contacts of the interrupter relay IR, tip contactsof the plug GP and jack 5 through the call bell at substation B, ring contacts of the jack J and plug .C P, alternate contact. 36 of relay IR, conductor 37, resistance 1" to ground. During each time ringing current is applied to the called line, the calling subscriber A will receive a revertive ringing tone which will notifyhim that the called subscriberzB is being signalled. This revertive tone is given over a circuit which is the same. as the ringing circuit just described up to 'point r from whence it may be traced through alternate contact 24 of relay RC, condenser K, normal contact 10 of relay LD, tip contacts of plug AP and jack J, through the receiver at the calling substation A, ring contacts of jack J and plug AP, normal contact 9 of 39, through the lower winding of relay AR to battery. The call bell at substationB will be intermittently actuated until the subscriber thereat removes his receiver from the switchhook whereupon ringing current will be automatically disconnected from thecal'led line, provided the called subscriber answers during a silent or non-ringing period, the ringing current being disconnected from the called subscriber line in the following manner: when the subscriber at substation B removes his receiver.

from the switchhook while the interrupter relay IR is in its de-energized position which. will be during a non-ringing or silent period, a circuit will be established for the calling supervisory relay CS, said'circuit being traced from battery through the lower windin of said rela CS normal contact 36 of relay IR, ring contacts of plug GP and jack J, through the now alternate closed switchhook contacts at substat on B, t1 contacts ct yack J andplug OP, norma con tact of relay IR, alternate contact 4L? cf .mally closedcontact17 of relay CS is the opening of the locking circuitof the ring; ing controlled relay RC, whereupon relay RC de-energizes and opens its alternate contact 26 thereby opening the vcircuit of the nect ringing current to the called for sub- RC die-energizing closes its normal contacts 524 and 25 whereby the conversational cir-- cuit. is closed through the talking conductors of the cord circuit C. The calling subscribe-r A and. called for subscriber B are now in conversational circuit.

Should. the calling subscriber A replace his receiver .upon its .switchhoolr. before the called for subscriber B responds ringing current will beautomatically disconnected from the called for subscribers line in the following manner: the answering supervisory relay AR will de-energize due to the opening of the circuit of relay AR at the alternate switchhook contacts of substation A. and relay AR de-energizing closes a circuit itor the link disconnected relay LD traced from battery through the winding of said relay LI), conductor 42, alternate contact 43 of relay SW, conductor 44, normally closed contact :11 of relay AR, c'onductor 45, alternate contact 46 of relay SW, conductors 47, 48 and 49, alternate contact 50hr" relay LS, conductor 51 to ground through alternate contact19 of relay SR.

Relay LD energizing over'this circuit opens its normally closed contact 29 thereby application of ringing current to the called for subscribers line is prevented. Relay LI) upon energizing also closes its alternate contact 4 which is adapted to close before normally closed contact 4 opens whereby a holding circuit is maini tained for relay LS traced from battery throughthe winding of relay LS, alternate contact 7 of said relay LS conductor 8, alternate contact 4 of relay LD, conductor 58, conductor 49, alternate contact 50 of relay LS, conductor 51, to ground through alternate contact 19 0f relay SR; Another result due to the energization of relay LD is the opening of normally closed contacts and 1c of said. relay 111D wine. trees the 'scriber line. The ringing controlled relay I calling subscribers line A from the cord circuit C whereby the calling subscriber A may be called or initiate another call, as the case may be, even though the plug AP remains in the jack J.

Should the operator at cord circuit C attempt to listen in on the conversation by operating her listening key RLK she is prevented from listening in due to the fact that relay SW7 will be energized, and will have its normally closed contacts 60 and 61 open, thereby preventing the operators set OR from being connected to the talking conductors of the cord circuit C when the listening key RLK is operated to its alternate position.

The subscribers A and B are now connected in conversational circuit and upon termination of conversation they will replace their receivers upon their respective switchhooks. hen the subscribers at substation E replaces his receiver upon its switchhook the circuit for the calling supervisory relay GS of the cord circuit C is opened whereupon said relay CS restores closing its normally closed. contact 17 wiereby the calling supervisory lamp CL will light over a circuit traced from battery through the said signal CL, normal contact 17 of relay CS, conductor 18 to ground through alternate contact 19 of relay SR. lVhen the calling subscriber Areplaces his receiver upon its switchhook, the circuit for the answering supervisory relay AR is opened whereupon relay AR de-energizes and closes its normally closed contact 11, whereby a circuit is closed for the link disconnect relay LD, said link disconnect relay LD upon. energizing opens its normally closed contacts 9, 10 and A to tree the calling subscribers line A from the cord circuit C, and at the same time establishes a holding circuit for the listening relay LS through its alternate contact 4 as traced above. A repetition of the tracing of the circuit for relay LD and also of the circuit for the listening relay LS is not deemed necessary as the circuits for these relays are clearly traced above. where a description was given of the operation of same when the calling subscriber A replaced his receiver upon its switchhook before the called subscriber responded. Relay AR de-energizing, a circuit is closed for the answering supervisory lamp AL traced from battery through said lamp AL, alternate contact 62 of relay SW alternate contact 43 of relay SW, conductor 44, normal contact 11 of relay AR, conductor 45, alternate contact 46 of relay SW conductors 47 and 48, conductor 49, alternate contact 50 of relay LS, conductor 51, to ground through alternate contact 19 of relay SR, over which circuit said lamp AL is caused to light. The operator observing the J and J respectively, whereupon the cord circuit C restores to normal, as do also the cut-oil relays CO and GO.

Operation of Fig. 1 and Fig. 2?.

Having described the operation of my cord circuit when used for interconnecting two subscribers lines at the same exchange, I will now describe the operation of my cord circuit when employed for connecting the subscribers substantion A with the subscribers substantion B at a distant exchange via my trunk circuit TC.

Assuming that the subscriber at substation A has initiated a call and that the same has been answered by the operator at the cord circuit C by inserting the calling plug AP into the jack J leading to the calling subscribers line, the operation of the cord circuit C in answering the call will be the same as described above. Assuming that it is the subscriber at substation D that is wanted by the calling subscriber A, the operator at cord circuit C upon learning this will converse over an order wire with the operator at the distant exchange to inform the distant exchange operator of the number of the called for subscriber D, whereupon the operator at the distant exchange will inform the operator at the cord circuit C which trunk to connect her cord circuit to, and assuming that the trunk indicated is the trunk TC, shown in Fig. 2, the operator will insert the calling plug Cl? into the trunk jack TJ, whereby relay SR of cord circuit C will energize in series with the relay E of trunk circuit TC over a circuit traced from battery through the winding of relay SR, through the winding ct relay R, sleeve contacts o1 plug Cl? and trunk jack TJ, through the winding of relay E to ground. Relay R will not operate when in series with the relay E of trunk circuit TC due to the high resistance of the winding of said relay E, and relay R- failing to energize, no circuit will be established for the relay SW of cord circuit C, whereby said relay SlV remains unoperated. When relay E of trunk circuit TC energizes the circuit is closed for the relav F traced from battery through the winding of said relay F, alternate contact of relay E to ground, and relay- F operating a circuit is established for supervisory signal TL provided plug Cl has not already been inserted into jack J said circuit being traced from battery through said signal TL, normal contact 71 of relay H, alternate contact 72 of relay F to ground. The signal TL lighting over this circuit will indicate to the operator at TC that the operator at cord circuit G has inserted the calling plug GP into the proper trunk jack of the trunk which has been assigned to the operator at the cord circuit. if the plug GP of trunk circuit TG has been inserted into the jack J before plug GP of cord G has been inserted into the jack TJ, relays SR and Hf;

for the lamp TL will be opened at normal.

contact 72 of said relay H whereupon said lamp TL i-s efiaced which will at this time notify the operator that the cord circuit G has been connected to the proper trunk circuit assigned. 7

' The operator at the distant exchange upon assigning the trunk to the operator at the branch exchange will operate her-listening key LK to connect her telephone head set TOR tothe trunk ci'cuit assigned and will test to determine the idle or busy condition of the called for subscribers line D and assuming that said line tests idle the'operator will insert the plug GP into the jack J Upon the insertion of the plug GP" into the ack J a circuit is closed "for relay SR; wiich will energize in series with the cut-off relay GO of line circuit L said cir' cuit being traced from battery through the winding of said relay SR sleeve contacts of plugs GP and jack J to ground through the winding of the cut-off relay G0 Relay GG operating will open its normally closed contacts thereby removing the line relay LE and line signal S from the control of the called subscriber D. Relay SE energizing closes a circuit for relay H, traced from batterythrough the winding of relay H alternate contact 73 of said relay SE to ground. Relay H energizing over this circuit will close its alternate contact 74: to extend the talking conductor of the trunk circuit TO to the called subscribers line D and will also open'its normally closed contact 71 and close its alternate contact 71..

The opening'of normal contact 71 of relay H opens the circuit ot the signal'TL whereupon said signal TL will be effaced. The operator at the cord circuit C having inserted a calling plug GP into'tlie trunk jack Til will now throw her key MRK to its alternate position, and leave the same in this position until the called subscriber answers, whereby normally closed contacts 21 and 32 oi said key are opened and alternate contact 21 will be closed. The operator will a now operate the plunger key of the ringing key BK corresponding to the proper trequency adapted to operate the call bell at the called: substation D and assuming that the trecuenc enerator G istlie nrooer" 1 b I L i. I frequency she-will depress the piunger bto its fully depressed pos tion thereby closing a circuit for the ringing interrupter relay IR traced from battery through the up- }per winding of said interrupter relay Il s,

conductor alternate contact 21 of key ll iRIQ conductor 22, the now closed contact 20 or the end spring of ringing key BK, conductor 23 normal contact 17 of relay GS, conductor 18 to ground through alternate contact 19 of relay SR. The interrupter relay IR will energize over this circuit [to connect ringing current to the called subscribers line so long as theplunger Z2 is in its fully depressed position. The circuit for the ringing current is as follows: ground through the rotating frequency generator G alternate contact or" 5 normal contact of plunger 6 conductor 34, alternate contact 35 of relay IR. tip contacts of plugs GP and trunk jack TJ, alternate contact'l lof relayl-l tip contacts of plug GP and' the operator the closed contact 20 05 the endspring of the ringing key RK will open whereby the energizing circuit for the interrupter relay IE will be opened, and

relay IE will restore to prevent further application of ringing current to the called subscribers line. In case the called for subscriber does not respond the operator at the cord circuit G will again depress the ringing key plunger F2 to its fullydepressed position to apply ringing current to the called subscribers line as just described above and will continue doing this at different intervals until the called subscriber answers. Another result due to the energization' of the ringing interrupter relay IR is the closure of the circuit for the ringing control relay RG traced from battery through the winding of said relay RC. conductor 8%,

alternate contact of relay IR, conductor 86, normal contact 17 of relay GS, conductor 18 to ground through the alternate contact 19 of relay SR. Relay- RG will energize over this circuit and remain energized so long asthe interrupter IE is in its ener-' gized position, said relay RG closing its alternate contact Qeto close a circuit over which a revertive ringing tone flow-s to the calling substationA to notify the calling subscriber at substation A that the called for subscriber at substation D is being signalled. The circuit for the revertive tone being 'tlie sa'me as the ringing circuit just described above up to the point r from which point r a portion 01": the ringing current will flow through alternate contact 24 of relay RC, over the tip side of cord circuit C, tip contacts of plug AP and ack J, through the receiver at substation A, ring contacts of jack J and plug AP, back over a portion of the ring conductor of cord circuit C and through the lower winding of relay All to battery and ground. The calling supervisory lamp CL will remain lighted until the called for subscriber atsubstation 1) removes his receiver from its switchhook whereby the operator by observing the lighted lam CL will know that the called subscriber at substation D has not responded and will apply ringing current to the called line by fully depressing her plunger 6 as pointed out above. lVhcn the called for subscriber answers when the relay is in its de-energized position a circuit will be closed for the calling supervisory relay CS traced from battery through the lower winding of said relay CS, normal contact 36 of relay IR, ring contacts of plug and jack TJ, ring conductor of trunk TC, ring contacts or plug CP and jack J through the now alternate closed switchhook contacts at the substation D, tip contacts of jack J and plug CP tip conductor of trunk TC, tip contacts of jack TJ and plug Cl normal contact 35 of relay IR, alternate con tact lO of relay SR, conductor ll to ground through the upper winding of said relay CS. Relay CS energizing over this circuit opens its normally closed contact 17 thereby opening the lighting circuit of the signal CL whereby said signal CL will be efiaced and the operator observing the unlighted signal CL will know that the called for subscriber at D has responded and will not depress the ringing plunger 6 again but will now restore the key MRK to normal, and the interrupter relay lltbeing in its deenergized position, ringing control relay RC will also be restored to normal position, and the calling and called subscribers at substations A and B, respectively, are conneeted in conversational circuit. Ringing current may also be connected to the called subscribers line so that the ringing current will be automatically and intermittently connected to said called line if it is so desired, and in this case the key MRK will not be operated, but the operator at cord circuit C will depress the ringing plunger 79 to its fully depressed position whereupon ringing current will be automatically and intermittently applied to the called subseribers line until the subscriber responds or the calling subscriber replaces his receiver upon its switchhook. lhe operation of the cord circuit for automatically and intermittently connecting ringing current upon depressing the plunger b is the same as that described when the cord circuit C is connected to the called subscribei"s line B and a repetition of this description is not deemed necessary for a clear understanding of this feature.

Assuming now that conversation has terminated and that the subscribers at substations A and D have replaced their receivers upon their respective switchhooks, the re placement oi the receiver upon its switchhook at substation A will open the circuit of the answering supervisory relay All, whereby a circuit will be closed for the recall rel/av traced as follows: battery 90, nern'ial closed contact 89 or the recall listcni" hey ELK. conductors 8 and 49, alternate center-t otrelay LS, conductor 51 to ground through alternate contact 19 relay SR. The link disconnect relay LD not being energizedand relay AR upon tie-energizing closes a lighting circuit for the answering supervisory lamp AL traced from battery through the lamp AL, normal contact 62 of relay S W, normal contact 46 of relay SW, conductor 45, normal contact 11 of relay All, conductor a l, normalcontact 4-3 of relay SW. conductors 47, l8 and 49, alternate contact 50 of relay LS, to ground through alternate contact 19 of relay SR. Upon the replacement of the receiver upon its switchhook at substation D the circuit for the calling supervisory relay CS -01. the cord circuit C is opened whereby said relay CS will tie-energize and close its normal contact 17, thereby closing the lighting circuit of the supervisory signal CL. The operator observingthe lighter signals AL and CL will know that the conversation has terminated and that the connection is no longer desired and will withdraw -the plugs AP and CP "from the jacks J and TJ respectively whereupon the cord circuit C restores to normal. The withdrawal of the plug Cl? from the jack TJ will open the energizing circuit of relay E of trunk circuit TC, whereupon said relay E will de-energize, and relay E deenergizing the circuit of relay F will be opened at alternate contact or" said relay E whereby said relay F restores and closes its alternate contact 72 thereby closing a circuit for the supervisory signal TL traced from battery through lamp TL, alternate contact 71 of relay H, normal contact 72 of relay F, over which circuit said lamp lights to notify the trunk operator that the plug CP of cord circuit C has been withdrawn from the jack T3 of the trunk circuit TC whereupon the tri ilk-operator will withdraw the plug GP from the ack J? whereby the trunk circuitTC is permitted 'to'restore to normal and is ready to be used for ex-' tending another call. I

Assuming now that the calling subscriber after. replacing his receiver uponiits switchhook on the termination of conversation removes his receiver. from its switchhook to initiate another call before the plug AP has been withdrawn from the jack J, the circuit for relay AR will again. be established to cause said relay AR to energize, and relay AR energizing closes its alternate contact 11 whereupon the inten'upter device I and relay PR are connected incircuit in series with the answering supervisorylamp AL, said circuit being traced from battery through the said signal AL,onormal contact 62 of relay 8 W, normal contact 46 of relay SIV, conductor 45, alternate contact. 11 of. relay AR, alternate contact 97 of relay.

RR, through the winding of relay PR and to ground through the live segments of the rotating interrupter device I. The supervisory lamp AL will be caused to flash'over this circuit due to the continuously rotating interrupterdevice I which opens and closes the circuit through said lamp AL. The operator observing the flashing of sig-' nal AL will know that. the subscriber at substation A has initiated another call and will operate her recall listening key ELK to its alternate position thereby opening the. locking circuit of relay RR at the normally closed contact 89 of said hey RLlQnand at the same time closes the alternate contacts 98 and 99 of said key RLK to connect the operators head set OR to the tallring coniduetors of the cord circuit C. Relay ER deener izes due to the opening of its locking circuit and restores to normal thereby opening its alternate contact 9'? to disconnect the interrupter device I out of circuit with the answering supervisory lamp AL whereby the signal AL will be eiiaced and the opera tor will inquire the wants of the calling sub scriber at substation A, and after learning the same; will restore her recall listening key ELK and take care of the call in the same manner as described in the foregoing specification.

lVhen the interrupter device I is connect: ed in series with the supervisory lamp AL and relay PR also being in series with the device I said relay will be intermittently operated, to open and close its alternate contact 100 whereby a circuit is closed 'for the pilot supervisory lamp PS which lamp PS will operate intermittently for supervisory purposes.

hile I have described and illustrated a preferred embodiment of my invention it ators cord circuit for interconnecting said calling and called subscriber lines and also for connecting said calling line with said trunkcircuit, an operators set, relay means for connecting and disconnecting said oper- 1 ators set-and said cord circuit, automatic means for freeing the calling subscribers line from said cord circuit if said cord circuit'is directly connected to a subscribers line, and means for rendering said automatic means inoperable if said cord circuit is connected to said trunk circuit.

2. In a telephone system, common battery telephone lines, a trunk circuit, a cord circuit for interconnecting two of said telephone lines in conversational circuit as a calling and a called line, said cord circuit also adapted to interconnect one of said telephone lines with said trunk circuit as a calling line, link disconnect means for freeing said calling line from said-cord circuit if said cord circuit is usedto directly connect common battery liIlBS,'JI18fiI1SIOI preventing the operation of said link disconnect means if said cord circuit is connected to said trunkcircuit, andautomatic signalling means in the 'said cord :circuit for signalhng the called subscriber 1f sa1d cord c1rcuit and said trunk circuit are used to connect to a called subscriber.

3. In a telephone system, common battery telephone lines terminating in an exchange,

a trunk circuit for extending any one of said lines as a calling line to a' distant exchange, a link circuit at said first exchange for interconnecting said telephone lines as calling and called lines, an operators set, re-' lay means for connecting and disconnecting sa1d operatorvs setand-sald link c1rcuit, automatrc means for freemg the calling hne from said link circuit it connection is establ'ished between common battery lines,

means for preventing the operation of saidautomatic means if said link circuit is con nected to sa1d trunk circuit.

4. A telephone systemincluding a'calling telephone line terminating in different operators positions in a telephone exchange, a called line terminating in the same exchange, a trunk circuit for extending a call from said exchange to' a distant exchange, a link circuit at each of said operators positions for seizing a call initiated over said calling line, an operators set, relay means same to li 'ht intermittentl to denote a re-' call if said link circuit is connected to said trunk circuit, and means for rendering said link disconnect means operable on a local connection and said last means inoperable on a trunk connection so that a call initiated over said calling line can only be answered by the operator that establishes the trunk connection.

5. A telephone system including a calling subscribers line, a called subscribers line, a trunk circuit, alink circuit for connecting said calling line to'said called line or to said trunk circuit, link disconnect means for said link circuit for freeing said calling line from said link circuit, a supervisory signal for said link circuit, means for causing said signal to operate continuously to denote a disconnection, means for causing said signal to operate intermittently to denote a recall, automatic means operable upon the connection of said link circuit to said called line to render said link disconnect. means operable and said third means inoperable, said automatic means being operable upon the connection of said link circuit to said trunk circuit for rendering said link disconnect means inoperable and said third means operable.

6. A telephone system including a calling line, a called line, a trunk circuit, a link circuit for connecting said calling line to said called line or to said trunk circuit, link disconnect means for said'link circuit for freeing said calling line from said link circuit, a supervisory lamp for said link circuit, means for causing said lamp to light continuously to signal for a disconnection, means for causing said lamp to light intermittently to denote a recall, electromagnetic means for said link circuit operable when said link circuit is connected to said called line to render said link disconnect means operable and said third meansinoperable, said electromagnetic means operable if said link circuit is connected to said trunk circuit to render said link disconnect means inoperable and said third means operable.

7. In a telephone system a calling telephone line terminating in multiple jacks and line lamps before a' plurality of operators positions, a link circuit for each of said operators positions for seizing a call initiated over said calling line, means for permitting ring said lamp to burn continuously only one operators link circuit to he opens tively connected to said calling line at the same time, calling jacks of different classes, link disconnect means operable, when the link circuit is operatively connected to said calling line and to a calling jack of one of said classes to automatically free the calling subscribers line from said link circuit to permit another call to be initiated and 'answered by any one of said operators, means for preventing the actuation of said link disconnect means when said link circuit is connected to a jack of the other of said classes so that a call over said calling line can only be answered by the operator at said link circuit so long as said link circuit remains connected to said calling line, a supervisory lamp for said link circuit, means for causnal for disconnection and to light intermittently to denote a recall.

8. In a telephone system, a calling line terminating in multiple answering jacks and line' lamps distributed among different operators positions, a called line, a trunk circuit, a link circuit at each of said operators positions for connecting said calling line or to said trunk circuit, means for permitting only one operators link circuit to be operatively connected to said calling line the i same time to seize the call initiated over said calling line, a supervisory lamp said link circuit, link disconnect means for freeing the calling line from said link cir-' cuit to permit another call to be initiated over said calling line and seized by any one of said operators when said link circuit is connected to said called line, means for areventing the actuation of said link disconnect means when said link circuit is connected to said trunk circuit so that a call initiated over said calling line prior to the disconnection of said link circuit from said calling line can only be answered by the operator controlling the link circuit, means for causing said supervisory lamp to light continuously to signal for a disconnection on either a local or trunk connection. and means for causing said lamp to light intermittently to denote a recall over said calling line on a trunk connection.

9. In a telephone system a calling subscribers telephone line terminating in a plurality of answering jacks at diiierent operators positions of a telephone exchange, a I

called subscribers telephone line terminating in calling jacks at said exchange, a

or for extending the same to said trnnk circuit, means for freeing the calling line from the link circuit operatlvely connected to said calling line when said link circuit is con link circuit is connected to said calling lineand trunk circuit. I

10. In a telephone system, acalling line terminating in an exchange at a plurality of operators positions, a called line termihating in said exchange, a trunk circuit terminating in said exchange, a link circuit at each of said operators positions for seizing a callinitiated oversaid calling line and for extending the same to sa-id called line or said trunk circuit, means individual to said link circuits for permitting only one operators link circuit to be operatively connected to said calling line at the same time, automatic means for freeing said calling line from the link circuit operatively connected to said calling line so that another call may he initiated over said line and seized by any one of said operators, means for preventing the operation of said link disconnect means Whenthe link circuit is operatively connected to said calling line and to said trunk circuit so that when a call is initiated over said calling line While said link circuit remains connected to said calling line said call will be seized by the same operator that seized the preceding call initiated over said calling line. i

11. In a telephone system a calling and a called subscribers telephone line terminating in a branch exchange, a link circuit for interconnecting said telephone lines, automaticdisconnect means for said link circuit and controlled over the calling subscribers line, a supervisory lamp for said link circuit,

a trunk circuit extending between said branch exchange and a distant exchange, said link circuit adapted to connect either of said lines to said trunk circuit as a calling line, means for preventing the operation of said automatiodisoonnect means when said link circuit is connected to said trunk circuit, and means for causing said supervisory lamp to light. continuously on either'a local or trunk connection to signal for a disconnection, and to light intermittently to dee note recall only when a trunk connection is established. 7

12. A telephone system including a calling telephone line and a called telephone lineterminating in an exchange, a trunk circuit extending from said exchange to a distant exchange, a link circuit for said first exchange for interconnecting said callmg and called lines, and also for connecting said calling line with said trunk circuit,

connected to said trunk circui.

a supervisory lamp for said link circuit, link disconnect means controlled by the calling subscriber for disconnecting said link circuit from said calling line when said link circuit is connected to a telephone line, means for preventing the operation of said link disconnect means when said link circuit is connected to said trunk circuit, means for causing said supervisory lamp to light continuously to signal for a disconnection, and

means for causing said lamp to light intermittently to denote a recall only when said link circuit isconnected to said trunk circuit.

13. A telephone system including a calling line terminating in multiple answering jacks and line lamps distributed among different operators positions, link circuits at each of said operators positions and adapted to permit only one link circuit to be operatively connected to said calling line at the same time to seize a call, said link circuits operable to establish a local connection or a trunk connection, a supervisory signal for each of said link circuits, means for causing said signal to operate continuously to signal for disconnection, a pilot supervisory signal for each of said positions and peratively associated with said link circuits at its associated position, means for causing said signal and said pilot signal to operate intermittently to denote a recall initiated over said calling line, electromagnetic means for each of said link circuits operable when a local connection is effected to render said link disconnect means operable to permit a recall'to be effected via said multiple line lamps even though the link circuit operatively connected to said calling line remains physically connected to said line, said electromagnetic means operable to render said link disconnect means inoperable, when a trunk connection is established, to cause said second means to operate so that arecall over said calling line will be indicated only at the operators position Where the trunk connection is es tablished. I

14. A telephone system including a calling line, a called line, a trunk circuit, a link circuit for connecting said calling line to said called line or to said trunk circuit, link disconnect means for said link circuit for freeing said calling line from sai" link circuit, a supervisory lamp for said link circuit, means for flashing said lamp for denoting a recall, electromagnetic means operable for rendering said link disconnect means operable and said second means inoperable When said link circuit is connected to said called line, said electromagnetic means also operable to render said link disconnect means inoperable and said second means operable when i said link circuit is Iii 15. A telephone system including a call ing line terminating in multiple jacks and line lamps, a called line, trunk circuit, a supervisory signal for said link circuit, link disconnect means for said link circuit operable to tree said calling line from link circuit so that a recall over said calling line will be signaled on said multiple line lamps, means for causing said signal to operate intermittently, electromagnetic means for said link circuit for rendering said disconnect means inoperable and to render said second means operable to cause a recall to be signaled by said supervisory signal. V

16. A telephone system including a calling line terminating in one exchange, a called line terminating in another exchange, a trunk circuit terminating in said first exchange in a terminal jack and at said second exchange in a terminal plug adapted to be connected to said called line, a link circuit at said first exchange for connecting said calling line to said trunk circuit via said terminal jack to extend said calling line to said called line, ringing current means at said first exchange for ringing the subscriber on said called line, and manual means and automatic means for applying ringing current to said called line.

17. A telephone s jstem including a calling line terminating in a telephone exchange, a called line terminating in a distant exchange, a trunk circuit extending between said exchanges and adapted to con-. nect to said called line, a link circuit at said first exchange for connecting said calling line to said called line via said trunk circuit, ringing current means at said first exchange, means for said link circuit for applying ringing current to said call d line either manually or automatically, a supervisory signal for said link circuit for signaling for a disconnection when the calling subscriber replaces his receiver upon its switchhook, and means for causing said signal to operate intermittently to denote a recall should a call be initiated over said calling line before the connection is taken down.

18. A telephone system including a calling telephone line, a called telephone line terminating in the same exchange, a called telephone line terminating in a distant exchange, a trunk circuit extending between said exchanges for extending a call from said first exchange to the called line at said second exchange, a link circuit for said first exchange for connecting said calling line to said first called line and also for connecting said calling line to said second callet line via said trunk circuit, automatic disconnect means for disconnecting said calling line from said link circuit when connected to a called line in the same exchange a supervisory signal for said link circuit, means for causing said signal to operate continuously to signal for a disconnection, and means for causing said signal to operate litermittently to denote a recall over said calling line when the same is connected to a called line at said distant exchange via said trunk circuit.

19. A telephone system including a calling line terminating in multiple jacks and line lamps in a telephone exchange, a called line terminating in said exchange, a trunk circuit, a link circuit for connecting said calling line to said called line or for connecting said calling line to said trunk circuit, supervisory signal for said link circuit adapted to operate continuously to signal for a disconnection, a pilot supervisory signal for each of said positions, means for causing said signals to operate intermittently to denote a recall initiated over said callline when said link circuit is connecting said calling line and said trunk circuit, and means for rendering said first means inoperable when said link circuit is connected to said calling line and said called line so that a recall initiated over said calling line is indicated by said multiple line lamps.

20. A. telephone system including a calling telephone line terminating in multiple jacks and line lamps at a telephone exchange, a trunk circuit, a link circuit for effecting a local connection of said calling line or a trunk connection of said calling line, a supervisory lamp for said link circuit, means for causing said lamp to light continuously to signal for a disconnection, automatic means for freeing said calling line from a local connection so that a recall initiated over said calling line will be indicated by said multiple line signals even though said link circuit remains physically connected to said line, and automatic means for causing saidlamp to light intermittently to denote a recall when a call is initiated over said line and a trunk connection is established for said calling telephone line. i

21. A telephone system including a calling telephone line terminating in a telephone exchange, a called telephone line terminating at said telephone exchange and a called telephone line terminating in a distant exchange, a link circuit for said first exchange for interconnecting said calling and called lines thereat, a trunk circuit for extending said calling line at said telephone exchange to said called line at saic distant exchange, said link circuit for said first exchange for connecting said calling line to said trunk circuit, a supervisory signal for said trunkcircuit at said second exchange for indicating a connection between said link circuit and said trunk circuit and also for indicating a disconnection or" said link circuit from said trunk circuit, said supervisory signal indicating the completion of the proper connection whether said trunk circuit is connected to or disconnected from the called subscribers line, a supervisory signal for said link circuit for signaling for a disconnection, and means efiective only when said link circuit is connected to said trunk for causing said last signal to operate to denote a recall initiated over said calling line prior to the disconnection of said link circuit from said calling line and said trunk circuit.

22. A telephone system including a link circuit provided with a connection terminal, manual and automatic ringing means for said link circuit, automatic disconnect means and flash recall means for said link circuit, connection terminals adapted to register with said link terminal, automatic means for rendering operative said disconnect means and said flash recall means ineffective when said link terminal is connected to one of said connection terminals, and automatic means for rendering operative said flash recall means and said automatic disconnect means ineffective when said link terminal is connected to another of said terminals.

23. A telephone system including a calling line and a called line terminating in the same exchange, a trunk circuit extending between said exchange and a distant exchange, an operators set for said link circuit, means for preventing said operators set from being connected to said link circuit when said link circuit is interconnecting said calling and called lines, means for permitting said operators set to be connected to said link circuit when said link circuit is interconnecting said calling line and said trunk circuit, ringing current means at the first exchange, and means for applying ringing current to the called line or to the trunk circuit either manually or automatically.

24. A telephone system including a calling telephone line terminating in multiple jacks and line lamps at a telephone exchange, a trunk circuit, a link circuit for eii'ecting a local connection of said calling line or a trunk connection of said calling line, an operators head set for said link circuit but normally disconnected therefrom, a supervisory lamp for said link circuit, means for causing said lamp to light continuously to signal for a disconnection, automatic means for freeing said calling line from a local connection so that a recall initiated over said calling line will be indicated by multiple line signals even though said link circuit remains physically connected to said line, and automatic means for causing said lamp to light intermittently to denote a recall when a call is initiated over said line and a trunk connection is established with said calling telephone line, means for preventing said head set from being operatively connected to said link circuit when a local connection is established, and means for connecting said head set to said link circuit when a trunk circuit is established.

Signed by me at Chicago in the county of Cook and State of Illinois, this 23rd day of June, 1923. V

MICHAEL B. STAZAK. 

